Mayor Marion Barry won the endorsement yesterday of 121 ministers representing many of the city's largest congregations, surpassing his support from clergy four years ago and adding what Barry termed a "moral" seal of approval to his candidacy for reelection.

The mayor said the support of the "moral leadership" of the city was important "because of the questions of integrity and honesty in government."

Barry was alluding to a series of corruption cases involving members of his administration in the past year. A recent Washington Post poll showed city residents are concerned about the integrity of D.C. government contracting officials.

About 75 of the ministers turned out for the endorsement ceremony yesterday at the Temple Church of God in Christ in Northwest Washington. In speeches emphasizing Barry's accomplishments, several ministers spoke of the need to avoid voter complacency.

"We want him to have an overwhelming victory," said the Rev. John Wheeler, pastor of the Vermont Avenue Baptist Church and chairman of the Religious Community Committee that has organized clerical support for Barry. "We can't have it if we sit home and say he is going to win. We want to give him a mandate."

Bishop Smallwood Williams, pastor of the Bible Way Church, praised Barry as a hard worker who is "entitled to another term in office."

Others supporting Barry include Bishop Walter McCollough, leader of the United House of Prayer for All People; the Rev. H. Beecher Hicks, pastor of Metropolitan Baptist Church; the Rev. Ernest Gibson, head of the Council of Churches of Greater Washington, and the Rev. A. Knighton Stanley, pastor of the Peoples Congregational Church, who supported Patricia Roberts Harris in the 1982 Democratic mayoral contest.

Barry was first elected in 1978 without much support from the clergy, while more than 100 ministers backed him in his 1982 reelection bid.

Last fall, a group of clergy joined Barry in opposing a referendum on the city's rent control law. Nevertheless, the referendum was approved narrowly by the voters.

"When I took on this job in 1978, a number of you were not supportive and that is why I feel so great today," Barry told the group. "When I took on this job I felt like David taking on Goliath . . . . Now this David has almost slain the Goliath -- that is, the Goliath who stands in the way of our people making progress."

Independent mayoral candidate Brian Moore said the clergy members' backing of the mayor "reflects badly" on them because it "is sort of a confirmation of their silence on the persistent impropriety that has been going on so long in this city."